Ford Expedition Temperature Sensor Malfunction
I have a 2003 Expedition with the 5.4L engine. During normal driving and at normal operating temperatures, the needle on the temperature gauge sits approximately in the middle. On a recent trip to the mountains, after driving at interstate speeds around 70mph I watched the needle on the temp gauge go from its normal position to the extreme hot (needle pegged) in approximately 2 seconds. Once the needle is pegged, an audible alarm sounds and the engine goes into limp mode, with a message telling you this in the message center. After pulling off the highway, there was absolutely no indication that the engine really is overheating. After switching the ignition off for approximately 1-2 min. and restarting the engine, the gauge goes back to its normal position and I can drive the vehicle again until the same thing happens. On a 2 hour trip, this can happen 3-4 times. I took it to my mechanic and after checking that the gauge was fine, he replaced the temperature sensor located in the block. This requires the removal of the intake manifold and is quite expensive. Assuming that the problem was fixed, I took it on another 3 hour trip and it was fine. However, on the return trip the same problem started again. I took it back to the mechanic and this time they cleaned out the radiator exterior of all dirt, grime, bugs, etc. and flushed the radiator. This had no effect and the same problem remains. I'm wondering if anyone else has any ideas. I'm starting to think perhaps the wiring to the sensor is bad, but the mechanic says he checked and everything looks fine. I know it's not beyond the realm to think the new sensor is bad, but since the problem is basically identical as with the old sensor, I have problems believing that. I do not think it is actually overheating since there is no visible sign of this (steam, overflowing fluid, etc.) and because I can continue to drive the vehicle without any problem immediately afterward and it doesn't overheat quickly. Any help would be appreciated.
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I have a 97 Expedition 4.6L with similar symptoms. The temperature appears to spike, but does it in a fraction of a second -- far faster than what would be physically possible. The engine never actually overheats, but appears to and then the truck goes into 'limp' mode. You pull over. Shut down. Wait. Start up and then you are good to go. Sometimes, the gauge goes back to normal before you hit limp mode and before you shut down. I've replaced the temp sensor as well. It seemed to do better for a bit, then went back to its old tricks. It seems that it is worse in stormy weather.
Every time you talk to a mechanic about it, they say "replace the thermostat. Flush the coolant." Been there, done that-- they don't hear you when you tell them "the truck is NOT overheating" The wires look good, but more and more, it seems like that must be the problem.
In the meantime, anyone want to buy a 97 Expedition?
I hope this isn't what your problem is. It seems like testing the wires should be relatively simple if that is the problem, so you might try that next.
I have been concerned that maybe I have something major like a cracked block or a head gasket on its way out. These symptoms seemed so odd that I was hoping that this problem was some simple $100 fix and I'd be on my way. Considering how long we've had this truck, I'm probably due for something big